How many strands make up a DNA molecule?
Answer
Two
How many strands make up a DNA molecule? Two strands make up the familiar DNA molecule. These long polynucleotide chains coil around each other into the famous double-helix shape, with the sugar-phosphate backbones on the outside and paired bases facing inward.
The two strands are complementary: adenine pairs with thymine, while guanine pairs with cytosine. They also run in opposite chemical directions, a property called antiparallel orientation. Together, these features let one strand serve as a template when DNA is copied before cell division.
The double-helix model was proposed in 1953 by James Watson and Francis Crick, drawing on crucial experimental evidence from Rosalind Franklin, Raymond Gosling, Maurice Wilkins, and others. Although DNA is usually discussed as double-stranded, some viruses have single-stranded DNA genomes. That exception does not change the standard answer for a typical DNA molecule in biology quizzes.